I am the Technical Rescue Duty Officer for the weekend and just received this from our EMO:

A conference call just concluded with the National Weather Service:
The snowfall forecast is now up to between 20 and 30 inches, with 30+ inches possible in higher elevations. Between 10pm tonight and 4am the forecasters are expecting 20 to 30 mph winds with snowfall that could be 2 to 3 inches an hour creating blizzard conditions. The liquid equivalent for this storm forecast is 2 to 3 inches of rain, which puts it as comparable to the largest storms of record for both Baltimore (President’s Day 2003) and Washington (Knickerbocker storm 1922).
Frederick County snow emergency plan went into effect at 9am, concurrent with Governor O’Malley’s declaration of a State of Emergency (attached). State and County highway staff have been pre-treating roadways since earlier this morning in preparation for the storm.
As a reminder for those organization who will be active during this emergency to track your costs carefully, as it is likely that there will be a disaster assistance request submitted by the Governor to FEMA. The last graphic on the email shows the “storms of record” for Baltimore and Washington. Forecasters are advising that the amount of precipitation could easily approach/break the record established by the “Knickerbocker storm” in 1922/President’s Day storm of 2003.
Additional status reports will be provided periodically throughout the storm. The next NWS conference call is at 6pm tonight.

Pete